Messages in this thread | | | Date | Mon, 22 Jan 2001 18:44:28 -0500 | From | Chris K Cockrum <> | Subject | Module Profiling Problem |
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I have been developing a driver for an audio card and encountered a problem which I have duplicated in the test code below. My problem is that when trying to profile a section of code in a kernel module I get erratic results. My cycle counts are sometimes 73xxx cycles more that I expect them to be. Does anyone know what could be causing this?
Thanks in Advance, Chris K Cockrum iBiquity Digital Corp. http://www.ibiquity.com
Running Linux 2.4.0 on a Tyan Tiger Dual 800MHz Motherboard w/133MHz Bus
#include <linux/kernel.h> #include <linux/module.h> #include <linux/sched.h> #include <asm/smplock.h>
/* Declare Spinlock */ spinlock_t testlock;
int init_module(void) { unsigned long long starttime,stoptime;
unsigned int lockflags,n,tempval=20000;
spin_lock_init(&testlock);
for (n=0;n<40;n++) { spin_lock_irqsave(&testlock,lockflags);
/* Clear Interrupt Flag */ __asm__ __volatile__ ("cli");
/* Get CPU Clock */ __asm__ __volatile__ ("rdtsc\n\t" \ "movl %%eax, (%%ecx)\n\t" \ "movl %%edx, 4(%%ecx)"\ ::"c" (&starttime));
/* Waste Time-Register Moves Looped tempval Times */ __asm__ __volatile__ ("loop: movl %%ecx,%%eax\t\n" \ " decl %%ecx\t\n" \ " jnz loop" \ :: "c" (tempval) : "%eax");
/* Get CPU Clock */ __asm__ __volatile__ ("rdtsc\n\t" \ "movl %%eax, (%%ecx)\n\t" \ "movl %%edx, 4(%%ecx)"\ ::"c" (&stoptime));
spin_unlock_irqrestore(&testlock,lockflags);
printk(KERN_DEBUG "Test: 0x%08X:%08X - %d Cycles\n", \ (unsigned int) (((stoptime-starttime)>>32)&0xFFFFFFFF), \ (unsigned int) ((stoptime-starttime) &0xFFFFFFFF), \ (unsigned int) ((stoptime-starttime) &0xFFFFFFFF) );
} return 0; }
void cleanup_module(void) { printk(KERN_DEBUG "Unloaded\n"); }
Results:
Test: 0x00000000:0000EA94 - 60052 Cycles Test: 0x00000000:0000EA87 - 60039 Cycles Test: 0x00000000:0000EA87 - 60039 Cycles Test: 0x00000000:0000EA87 - 60039 Cycles Test: 0x00000000:00020977 - 133495 Cycles Test: 0x00000000:0000EA87 - 60039 Cycles Test: 0x00000000:0000EA87 - 60039 Cycles Test: 0x00000000:0000EA87 - 60039 Cycles Test: 0x00000000:0000EA87 - 60039 Cycles Test: 0x00000000:0000EA87 - 60039 Cycles Test: 0x00000000:0000EA87 - 60039 Cycles Test: 0x00000000:00020997 - 133527 Cycles Test: 0x00000000:0002098F - 133519 Cycles Test: 0x00000000:0000EA87 - 60039 Cycles Test: 0x00000000:0000EA87 - 60039 Cycles Test: 0x00000000:0000EA87 - 60039 Cycles Test: 0x00000000:0000EA87 - 60039 Cycles Test: 0x00000000:00020976 - 133494 Cycles Test: 0x00000000:0000EA87 - 60039 Cycles Test: 0x00000000:0000EA87 - 60039 Cycles Test: 0x00000000:0000EA87 - 60039 Cycles Test: 0x00000000:0000EA87 - 60039 Cycles Test: 0x00000000:0000EA87 - 60039 Cycles Test: 0x00000000:0002098A - 133514 Cycles Test: 0x00000000:0000EA87 - 60039 Cycles Test: 0x00000000:0000EA87 - 60039 Cycles Test: 0x00000000:0000EA87 - 60039 Cycles Test: 0x00000000:0000EA87 - 60039 Cycles Test: 0x00000000:0000EA87 - 60039 Cycles Test: 0x00000000:0000EA87 - 60039 Cycles Test: 0x00000000:0002098E - 133518 Cycles Test: 0x00000000:0000EA87 - 60039 Cycles Test: 0x00000000:0000EA87 - 60039 Cycles Test: 0x00000000:0000EA87 - 60039 Cycles Test: 0x00000000:0000EA87 - 60039 Cycles Test: 0x00000000:0000EA87 - 60039 Cycles Test: 0x00000000:0000EA87 - 60039 Cycles Test: 0x00000000:0000EA87 - 60039 Cycles Test: 0x00000000:0002098A - 133514 Cycles Test: 0x00000000:0000EA87 - 60039 Cycles
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